The alloys of Al—Cu—Mg—Li type are widely used in the aircraft and aerospace industries. Well-known are the American alloys having the chemical composition as follows (in mass %):
Li1.9-2.6Cu1.0-2.2Mg0.4-1.4Mn  0-0.9Ni  0-0.5Zn  0-0.5Zr  0-0.25Al-balance(1)Li1.5-2.5Cu1.6-2.8Mg0.7-2.5Zr0.05-0.2 Fe≦0.5Si≦0.5Al-balance(2)
The abovesaid alloys while having reduced density and acceptable mechanical properties in the course of single- and repeated loading, are highly sound-conductive upon acoustic influence. For some aircraft and aerospace vehicles the sound absorbing properties are predominating.
Also known is the Russian alloy 1441 having the chemical composition as follows (mass %):
Li1.7-2.0Cu1.6-2.0Mg0.7-1.1Zr0.04-0.2 Be0.02-0.2 Ti0.01-0.1 Ni0.01-0.15Mn0.01-0.4 Ga0.001-0.05 H1.5 · 10−5-5.0 · 10−5                at least one element from the group        comprising:        
Zn0.01-0.3Sb0.00003-0.015 Na0.0005-0.001Al-balance(3)
Said alloy is attractive in providing an improved combination of strength and plasticity. The sheet made of this alloy has the following properties: σβ≧410 MPa, σ0.2≧305 MPa, δ≧7%, Kapp≧100 MPa√m. Nevertheless, the aircraft skin made of said alloy has a sound-absorbing property which is not high enough.